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Rainwater harvesting

  • 03-05-2021 3:23pm
    Registered Users Posts: 10,311 ✭✭✭✭

    Hi all,
    I am getting a garden shed in the next couple of weeks and I want to get a rainwater harvesting system in place to water the raised bed hoop house I've put in for growing veg.
    Has anyone set something up like this before and have they got any advice?
    Was thinking of using black ibc totes and some filters etc on the downpipes.

    It's be nice to have a water source when we inevitably get water shortages later in the year.


  • Registered Users Posts: 6,583 ✭✭✭The Continental Op

    What I would do if I had the space is use say a 220l barrel attached at the top to a IBC.

    Rainwater goes into the 200l barrel and keeps it nearly full and then goes into the IBC. Most of the sediment will stay in the barrel which can be tipped up and washed out occaisionally.

    As it is I have several 220l barrels connected with one inch fittings.

    Wake me up when it's all over.

  • Registered Users Posts: 32,634 ✭✭✭✭Graces7

    At one house I had an ( enclosed) rainwater tank fed from the gutters, and pipes across to my polytunnel and main garden. It was excellent.

  • Registered Users Posts: 10,311 ✭✭✭✭tom1ie

    Graces7 wrote: »
    At one house I had an ( enclosed) rainwater tank fed from the gutters, and pipes across to my polytunnel and main garden. It was excellent.

    That sounds interesting.
    Was the tank inside in case of frost?
    What size tank we talking about graces? IBC tote or rain barrell?
    Did you have the pipes over to your poly tunnel underground?

  • Registered Users Posts: 6,675 ✭✭✭zg3409

    When water charges came in I researched collecting rainwater. As suggested freezing is an issue, even insulation is no good unless you have a heat source to prevent freezing over multiple days. Ideally you have underground storage. If used for drinking you need really good cleaning system with possibly UV lights. I toyed of the idea of feeding untreated rainwater to the likes of toilets and showers with a backup of mains in case of no rain for many weeks.

    It seemed like a lot of work at with no water charges does not make financial sense.

    I suggest maybe adding a second water tank in the attic, in series with the first one. That will give you double the local tap water reserve in case of burst mains nearby etc. If you feed the fresh tap water into one tank, and take the water out if the other tank, it should allow enough movement in both tanks so the water does not stagnate. I think its impractical to collect rain water for drinking unless you are off grid and off the mains supply. If water was charged for then you could do some sort of justification.

    In the real world we use a massive amount of water daily and a few hundred litres of storage won't last long unless you ration it by not showering etc.

  • Registered Users Posts: 851 ✭✭✭Boardnashea

    I have recently bought two IBCs which I want to install off our large shed. As The Continental Op suggests I am going to use the existing water butt as a simple sediment filter and then into the IBCs in series. I won't have frost protection so I might drain them during the winter although the water butt has never had a issue with frost (5 years at least).

    I will try and raise the whole system by about 1M to give a decent head of pressure for the tunnel hose.

    I'm sure it would be great to bury the line going to the tunnel but knowing my timetabling it will be lying on the ground for the first 5 years at least. Once water is flowing other priorities will take over.

    I would also like to get a small pump organised to get water back up into the main tank in the attic. Main advantage is we live in a hard water area so the collected water will reduce wear on our washing machine, reduce shampoo, soaps etc and we are also flushing treated water down the toilet every day which doesn't make sense, even if I was not paying for it personally (I am paying for it because we are on a group scheme).

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  • Moderators, Science, Health & Environment Moderators Posts: 5,000 Mod ✭✭✭✭spacetweek

    Hi everyone sorry to bump this thread.

    I am thinking of buying this tank in order to collect water for my downstairs toilet. Not going to supply anything else so probably doesn't need filtering or UV. Anyone installed one of these before?

    Do you think pressure would be an issue? I'd install the tank up the wall a bit so the toilet it feeds would be lower. Do toilets still refill when the water pressure is low?

    Was thinking of having a 3-way valve inside the house so I could select between feeding the toilet from the attic or the rain tank. Anyone tried doing that before, is it straightforward?

    Anything I should know about putting a pipe through the wall to service the toilet, would that damage the house insulation or anything?

  • Registered Users Posts: 6,583 ✭✭✭The Continental Op

    Firstly that may be illegal because of the 3 way valve but no one will care. If there is the slightest possibility of non potable water ending up in the watermain then its not allowed. Anyway the main point I wanted to make was that with traditional ball cocks you can change the valve seat to one with a bigger orifice so it fills more quickly.

    Edit> Another thought is that many toilet cisterns have the option of having the water feed from either side. So you could have two ballcock fittings (if there's room) and just turn on the relevant feed. This might fit?

    Another point: You can really install that unit too far up a wall as it says the base must be supported! Check the installation instructions.

    Post edited by The Continental Op on

    Wake me up when it's all over.

  • Registered Users Posts: 6,954 ✭✭✭10-10-20

    Yes, pressure will be an problem as the tank empties. It needs to be as high as possible. It also needs good filtering as you don't want to block-up the valves, etc.

    Drilling through the wall isn't a major issue, just back-fill the holes on both sides and you'll be fine. Depending on the point where the pipe will enter the house, you may need to drill from the inside-out to keep the hole tidy and it also keeps much of the dust out from between the insulation and inner-wall.

  • Registered Users Posts: 851 ✭✭✭Boardnashea

    Hi Spacetweek

    The tank looks really tidy (at a huge price), but my concern with it would be frost damage. It has a huge surfaced area, and that may make it more likely to freeze and expend.

  • Moderators, Science, Health & Environment Moderators Posts: 5,000 Mod ✭✭✭✭spacetweek

    Thanks for response.

    The plan would be for the 3-way valve to be in the under-stairs cupboard which is on the ground floor and right behind the toilet. So not remotely near the attic cistern - I don't see how rainwater could ever end up mixing with the mains.

    Unfortunately the toilet cistern only has intake on the bottom so no possibility of a second intake, hence the 3-way valve idea.

    I'm planning on laying bricks under the tank to support it. I've read the instructions. When full the tank will weigh 250 kg that's a quarter of a tonne! It'd certainly need to be supported and not just hanging off a wall!

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